To adequately prepare military personnel, good military training must account for and simulate not only the use of hand grenades, but also their explosive fragmentation characteristics. To do this, it is necessary to have practice hand grenades for use in war games. An example of a war game marking grenade is disclosed in U.S. Pat. No. 4,944,521. Briefly, a number of paintballs are press-fit or glued into cavities formed in the grenade housing with each paintball extending partially outside the confines of the grenade housing. A compressed gas cylinder provided in the housing is pierced when the grenade is activated. The gas is directed within the grenade housing to a plurality of plugged channels, each of which leads to one cavity holding a paintball. When sufficient pressure builds in each plugged channel, the plug is propelled forward to impact the paintball such that the plug and paintball are ejected from the grenade housing.
The problems associated with the hand grenade disclosed in U.S. Pat. No. 4,944,521 are numerous. Since the paintballs extend beyond the confines of the grenade housing, premature rupturing of the paintballs can occur during handling of the grenade. Also, because each paintball extends partially outside the grenade housing and resides at the end of a plugged channel in which launch pressure is developed, each paintball is only exposed to launch pressure for a very brief time period. That is, once pressure in each plugged channel is sufficient to overcome frictional forces holding the plug and paintball in position, the paintball is immediately expelled from the grenade housing while the pressurized launch gas quickly expands. This limits the amount of acceleration each paintball can develop so that the range of each paintball is only a few feet. Since real grenades have ranges much greater than a few feet, realistic practice results cannot be achieved. Finally, since each paintball is impacted with a propelled plug, the paintball can fracture from the impact and, therefore, never be ejected in whole from the grenade housing.